In relation to a semiconductor manufacturing device for forming a thin film, it is required to control process gas yielded as a main fluid by vaporizing a liquid at 250° C. or more. For flowing the process gas yielded by vaporizing the liquid at 250° C. or more while controlling to maintain the temperature of 250° C. or more, a resin valve having a resin valve seat and a resin diaphragm can not be used. Heretofore, three poppet valves are used to connect three passages by metal-to-metal contact between a metal valve seat and a metal diaphragm.
However, the three poppet valves connected by the metal contact have a problem that connecting portions could wear due to repetition of the metal contact action. The wear causes leakage of the process gas and generation of abrasion powder that contaminates the chamber, thus shortening lifetime of the switching valve.
On the other hand, another conventional technique of a switching valve utilizing purge gas instead of the metal contact connection is disclosed as a rotary switching valve in Patent Literature 1.
The rotary switching valve in Patent Literature 1 includes: a valve body formed with a main passage for flowing a main fluid; and a cylindrical valve member rotatably held in the valve body and formed inside with a main passage. The cylindrical valve member is rotated to switch the main passage. The rotary switching valve in Patent Literature 1 is used for air-transporting polyethylene, polypropylene, and others in a form of powder particles.
In the rotary switching valve of Patent Literature 1, purge gas is supplied into a clearance or gap between the valve body and the cylindrical valve member to air-transport the powder particles. The flowing purge gas flicks the powder particles before the powder particles flowing through the main passage in the cylindrical valve member are caught in the clearance between the valve body and the cylindrical valve member. The flowing purge gas can thus prevent the powder particles from becoming caught in the clearance between the valve body and the cylindrical valve member.